The invention relates to the field of motor vehicles and more specifically to a brake fluid reservoir supplying the hydraulic brake and clutch circuits.
In a general manner, a hydraulic brake circuit comprises a brake fluid reservoir containing a hydraulic fluid, this fluid being intended to transmit a hydraulic pressure to the brakes of the front and rear wheels that is formed by the movement of a piston in a master cylinder when the driver of the vehicle actuates a braking means, for example the brake pedal.
There are other hydraulic systems in motor vehicles, particularly the clutch, which can use the same hydraulic fluid as the hydraulic brake circuit. In order to simplify the hydraulic circuits, a common hydraulic fluid reservoir is used for both circuits, namely for the brake circuit and for the clutch circuit. These reservoirs are typically made of plastic in the form of two shells assembled by welding.
Since the hydraulic absorption of the brake circuit increases with wear on the friction elements, there is a progressive loss of brake fluid, which means that brake fluid should be periodically added to the reservoir so as to keep a substantially constant fluid level in the brake fluid reservoir. By contrast, wear on the clutch usually results in hydraulic fluid being driven back into the reservoir. There is thus a transfer of hydraulic fluid from the reservoir toward the brake. If a common hydraulic fluid reservoir is used for the brake circuits and the clutch circuits, there may occur a progressive transfer of hydraulic fluid from the clutch toward the brake. This liquid may be loaded with solid, metal or non-metal, particles or debris which detach, by abrasion or any other mechanism, from the metal walls with which the fluid is in contact. The largest dimension of these particles or debris is typically between 100 and 500 μm.
They can be entrained into the brake circuit, where their presence is particularly undesirable. Specifically, anti-lock braking systems (ABS) typically include electronically operated valves which are generally solenoid ball valves; these solenoid valves can become impaired when solid particles or debris passes through them. Similarly, an ABS-type system includes seals which are liable to become impaired if they come into contact with solid particles or debris.